Now to a developing story about a major Supreme Court case. NPR has previously reported that the Obama administration would file a Friend of The Court Brief, urging The Court to strike down a ban on same-sex marriage in California. Well, today is the deadline to file that brief but it has not yet been filed.

NPR legal affairs correspondent Nina Totenberg is here to explain what we may expect to come in the brief and why its significant. And first of all, Nina, remind us how this case came about.

NINA TOTENBERG, BYLINE: Well, in 2008 California voters narrowly approved a referendum that banned same-sex marriage. A federal district court subsequently struck down the law as unconstitutional discrimination. An appeals court later ruled it invalid on narrower grounds. And the State of California, under Republican and Democratic governors, has refused to defend the law in court, and so the sponsors of the referendum appealed to the U.S. Supreme Court. In the meantime, gay marriage has remained illegal in the state.

CORNISH: So, you reported two weeks ago that even though the administration didn't have to get involved in this case, it had decided that it should file a Friend of The Court Brief, and that it would side with same-sex marriage advocates. But that still left questions about what argument the administration would make, right?

TOTENBERG: That's right. And we still don't know for sure what argument the administration is going to make in that brief. But we know pretty much what the choices are.

CORNISH: OK, let's go for it. What are they?

TOTENBERG: So, choice number one, door number one: is a broad argument that would urge The Court to declare that gay couples have a constitutional right to marry. And if The Court agree with that, that would strike down laws banning same-sex marriage in more than 30 states.

Choice number two is to urge The Court to take a position that would invalidate the California ban but only the California ban. And that's based on the fact that California at one point legalized same-sex marriage and then took that right away.

And the third choice, number three, is a middle ground that would urge the justices to take one step at a time, leaving open the possibility that The Court would one day invalidate all state bans, but that it hasn't gotten there yet.

CORNISH: So what is this middle ground? I mean how do you do that?

TOTENBERG: Well, California, like eight or nine other states, has a law that guarantees all the same rights to gay couples as heterosexual couples, all the same rights except marriage. And there's an argument that says, look, if you guarantee these couples everything except the right to marry, you're labeling same-sex couples as somehow inferior; you're discriminating against them for no rational reason.

After all, marriage is a civil action, performed and authorized under state law. It's not a religious action. Religions can and do ban gay marriage or marriage for people who a divorced, for example - but you get my drift. Religions can do that. States, in general, can't unless they can articulate a constitutional reason. And the argument is that there's no such reason when you're already guaranteeing gay couples every other right.

CORNISH: Now, Nina, you also reported a couple of weeks ago that the president would make this decision. Do you know if he did?

TOTENBERG: He did, or so I'm told. After all, don't forget he taught constitutional law. But I am told that he didn't make the decision until yesterday.

(LAUGHTER)

TOTENBERG: Which makes it sort of close for the Department of Justice.

CORNISH: So what's your best bet on what choice he made?

TOTENBERG: I think he sort of signaled a somewhat cautious approach a few days ago, in an interview when he said he had to be careful, essentially not to get too much into The Court's business - although he personally believed in the right of marriage. So my best bet is the middle ground, while at the same time, the brief is likely I think to signal that ultimately The Court may want to strike down all laws, it doesn't have to do that right away.

CORNISH: So it's sort of like having your cake and eating it too?

(LAUGHTER)

TOTENBERG: Exactly, but it leaves all options open. And when you're dealing here with a pretty conservative Court majority that might be the smart option, and even some gay rights advocates privately agree with that assessment.